Background: Posttraumatic stress disorder (PTSD) is a worldwide problem that is a common consequence of trauma. PTSD is often comorbid with depression. Despite the availability of medications and psychotherapy, many persons with PTSD experience persistent symptoms. Veterans frequently use Complementary and Alternative Medicine (CAM) interventions to augment their traditional care and to address their social and spiritual needs. The proposed controlled randomized trial will assess whether a novel CAM intervention, Loving-kindness Meditation (LKM), is not meaningfully inferior to another group-based PTSD treatment , Cognitive Processing Therapy (Cognitive Only version; CPT-C) for reductions in PTSD and depressive symptoms. Promising results from an open trial of LKM completed in our laboratory with male and female Veterans with PTSD suggest that LKM is feasible and safe Veterans with PTSD, and is associated with significant improvements in PTSD symptoms and depression, as well as enhanced self-compassion. In the proposed project 170 Veterans with PTSD will be randomized to LKM or CPT-C. Comprehensive assessments will be performed at baseline as well as at the end of the 12-week interventions and 3 and 6 months later. PTSD symptoms, depression, posttraumatic maladaptive cognitions and self-compassion will be assessed weekly during the treatment phase to assess temporality of change and to assess mediators of outcomes. Specific Aims: Aim 1: Evaluate if LKM is non-inferior to CPT-C in producing reductions in PTSD symptoms among Veterans with current PTSD. Aim 2: Evaluate the non-inferiority of LKM and CPT-C in producing reductions in depressive symptoms among Veterans with current PTSD. Exploratory Aim: Evaluate potential mediators of response to LKM and to CPT to provide preliminary information regarding whether they are consistent with the mechanisms of change conceptualized by each intervention to be associated with improvement in PTSD and depression. Design: A randomized controlled non-inferiority trial comparing LKM to CPT-C. Participants: 170 male and female Veterans with current PTSD. Intervention: 12-week group-based LKM or CPT-C. Hypotheses and Analyses: Veterans randomized to LKM will report mean reductions in PTSD and depressive symptom severity that are not meaningfully worse than CPT-C. We further hypothesize that reductions in posttraumatic maladaptive beliefs will more strongly mediate PTSD and depressive symptom improvement for those assigned to CPT-C than those assigned to LKM. Implications: If improvement in outcomes for LKM are non-inferior to CPT-C, the findings of this trial would support offering LKM as an additional group-based treatment for Veterans with PTSD.